Affinity Partitioning
The potential applications for biologically active proteins have greatly increased. Commercial implementation of this technology now frequently depends on the ability to isolate these substances at reasonable cost. Until recently, separation technology which could support industrial applications was limited to filtration and centrifugation. However, these techniques are extremely dependant upon particle size and therefore approach their limit of usefulness during the harvest of even small intact microorganisms. The problems encountered are therefore greatly increased during the attempted isolation of intracellular components from ruptured cells where component size is, of course, greatly reduced.
The process of affinity partitioning using two phase aqueous systems has been suggested for some separations. Affinity partitioning basically involves the formation of multiple, distinct phases in a common solvent following the addition of materials, such as polymers, which produce immiscible phases when in solution and the selective affinity of a molecule for one phase over the other. The partition coefficient of a system is defined as the concentration of a specific material in the upper phase divided by its concentration in the lower phase of the system. It therefore describes the ability of a system to selectively concentrate a given material in one phase of the system. Aqueous two phase systems have been known since the late nineteenth century from the work of Beijerinck who published his findings regarding aqueous phase formation with agar and gelatin. As it is not dependant upon particle size as are conventional techniques such as filtration and centrifugation, affinity partitioning offers the potential of improved recovery of cellular components in industrial scale recoveries. The use of affinity partitioning in the isolation of enzymes from other cellular matter is disclosed in U.S. Pat. No. 4,144,130. Affinity partitioning technology has further been employed to date in the recovery of interferon (U.S. Pat. No. 4,343,735), the isolation of human coagulation factors VII and VIIa (U.S. Pat. No. 4,470,969) and the isolation of deoxyribonucleic acid (U.S. Pat. No. 4,207,200).